Method and device for detecting vertical bell laboratories layered space-time codes

ABSTRACT

The present invention discloses a V-BLAST detection method for a MIMO system, including: a first detecting step for acquiring in sequence the old detection components of a transmitting symbol vector with the optimum ordering-successive interference cancellation detection method; a second detecting step for taking the detection component with the highest space diversity degree among the old detection components as a first new lo detection component, and acquiring in sequence the other new detection components of the transmitting symbol vector in an inverse order of the optimum detection order with the optimum ordering-successive interference cancellation detection method; an outputting step for outputting the first new detection component and the other new is detection components as the final detection result. The method according to the invention employs the outer close loop iteration technology to further reduce inter-layer error propagation of V-BLAST. This method has less complexity.

CROSS-REFERENCE TO RELATED APPLICATIONS(S)

This application is based on the Chinese Patent Application No.200410017647.1 filed on Apr. 13, 2004, the disclosure of which is herebyincorporated by reference thereto in its entirety, and the priority ofwhich is hereby claimed under 35 U.S.C. §119.

TECHNICAL FIELD

The present application relates to the field of wireless communication,in particular to a method and a device for detecting Vertical BellLaboratories Layered Space-Time (V-BLAST) codes.

BACKGROUND ART

With the development of wireless communication technology anddiversification of information demands, people gradually transfer theirattention from pure voice services to multi-media services. However,different from wire communication, wireless communication is restrictedby various factors such as spectrum resource, transmission power andmulti-path fading, among which the spectrum efficiency becomes a focusof attention because it directly affects the capacity of a wirelesscommunication system.

In order to improve the spectrum efficiency of a wireless communicationsystem, a Multiple Input Multiple Output (MIMO) system is proposed,wherein a plurality of transmitting antennae and a plurality ofreceiving antennae are used to transmit and receive the signals. FIG. 1illustrates a MIMO system by taking a V-BLAST scheme with M transmittingantennae and N receiving antennae as an example.

As shown in FIG. 1, there are M transmitting antennae and N receivingantennae in the MIMO system, where 1<M≦N. An information bit streamtransmitted by a signal source forms M data sub-streams by channelencoding, constellation modulation and serial/parallel conversion.During the same symbol interval, the parallel M data sub-streamsconstitute a transmitting symbol vector a. The data sub-streams, whichrespectively correspond to the components a₁,a₂, . . . ,a_(M) of thetransmitting symbol vector a, are transmitted by M transmitting antennaerespectively, and received by N receiving antennae after passing throughspace channels in a scattering environment. The obtained receivingsymbol vector r is transmitted to a signal target after V-BLASTdetection, parallel/serial conversion, constellation demodulation andchannel decoding. Since the M data sub-streams are transmitted to thechannels simultaneously, they occupy the same frequency band. Therebythe capacity and the spectrum efficiency of a wireless communicationsystem can be remarkably improved without bandwidth increasing.

To make a full use of the channel space of a MIMO system, peopleproposed different schemes of space-time process, among which the mostremarkable one is a system model of layered space-time code, i.e. theVertical Bell Laboratories Layered Space Time (V-BLAST) code, which isproposed in 1998 in an article (hereinafter referred to as D1) titled“V-BLAST: An Architecture for Realizing Very High Data Rates Over theRich-Scattering Wireless Channel” by Wolniansky, Foschini, Golden andValenzuela. No code circulation phenomenon appears among the antennae ofthis V-BLAST. The separation and cancellation method of a receiver is aniteration method that selects the optimum signal-to-noise ratio (SNR)and linearly weights receiving symbol vector, which simplifies thereceiving process greatly. Therefore, a MIMO system based on V-BLASTtechnology increasingly becomes a focus of study.

It can be seen from FIG. 1 that the information transmission of thewhole MIMO system based on V-BLAST technology realizes high spectrumefficiency and large capacity via a plurality of transmitting antennaeand a plurality of receiving antennae. The key step in the wholeprocessing scheme is the serial/parallel conversion and the V-BLASTdetection. However, in a MIMO system based on V-BLAST technology, sinceV-BLAST codes get in return high band efficiency at the cost of partialdiversity gain, the V-BLAST detection method for signal detection usedin the receiving side is crucial to the improvement of the performanceof the whole system.

The V-BLAST detection method disclosed by the above D1 is a detectingmethod based on the optimum ordering-successive interferencecancellation (Ordering-SIC). Within a symbol time, this method usesa₁,a₂, . . . ,a_(M) to respectively represent the components of thetransmitting symbol vector a transmitted from the transmitting antennae.The receiving symbol vector r corresponding to the transmitting symbolvector may be represented as:r=H·a+v  (1)

where H is a channel matrix of N×M, a=(a₁,a₂, . . . ,a_(M))^(T) standsfor the transmitting symbol vector, i.e. a vector having M rows and 1column obtained by transposing the vector (a₁,a₂, . . . ,a_(M)), v is acolumn vector of N×1, indicating an additive white Gaussian noise.

Furthermore, a detection sequence is set as:S≡{k ₁ ,k ₂ , . . . ,k _(M−1) ,k _(M)}  (2)

wherein k₁,k₂, . . . ,k_(M−1),k_(M) is a certain permutation of M, M−1,. . . , 2, 1, representing an optimum detection order.

The first decision estimated value y_(k) ₁ can be firstly obtained byusing the aforesaid Ordering-SIC V-BLAST detection method.y _(k) ₁ =w _(k) ₁ ·r ₁  (3)

wherein w_(k) ₁ is a zero-forcing vector, r₁ is the first receivingsymbol vector of the receiving symbol vector r, the initial value is rper se, then the first decision estimated value y_(k) ₁ is a linearcombination of the zero-forcing vector w_(k) ₁ and the aforesaidreceiving symbol vector r.

Then, a first detection component â_(k) ₁ of the transmitting symbolvector is obtained:â _(k) ₁ =Q(y _(k) ₁ )  (4)

wherein Q(y_(k) ₁ ) represents the constellation demodulation of thefirst decision estimated value y_(k) ₁ .

After that, assuming â_(k) ₁ =a_(k) ₁ a_(k) ₁ is cancelled from thereceiving symbol vector r to obtain the second receiving symbol vectorr₂:r ₂ =r ₁ −â _(k) ₁ (H)_(k) ₁   (5)

wherein (H)_(k) ₁ stands for the k₁th column of H, r₁ is the firstcomponent of the receiving symbol vector r, and the initial value is rper se.

Then, the second receiving symbol vector r₂ is used to replace r₁, andthe above steps (3) to (5) are repeated to obtain the second detectioncomponent â_(k) ₂ of the transmitting symbol vector and the thirdreceiving symbol vector r₃. The rest may be deduced by analogy till theM-th detection component â_(k) _(M) of the transmitting symbol vector isobtained.

In this method, a key vector is the zero-forcing vector w_(k) ₁ used instep (3). The methods of calculating the zero-forcing vector w_(k) ₁include a minimum means-square error (MMSE) detecting method and azero-forcing (ZF) detecting method, the latter being simpler.

Below we take the ZF method as an example to explain in detail the stepsof calculating zero-forcing vector and performing V-BLAST detection inthe Ordering-SIC V-BLAST detection method disclosed by D1.

Fist of all, initialization starts:Making G₁=H⁺  (6){tilde over (H)}=H  (7)r₁=r  (8)i=1  (9)

wherein, H⁺ represents a Moore-Penrose pseudoinverse matrix of channelmatrix H, r is the receiving symbol vector represented by the aboveequation (1).

After that, iteration steps 1) to 6) are executed as follows:

1) determining the sequence number k_(i) of detection symbol;

$\begin{matrix}{{k_{i} = {\underset{j \notin {\{{k_{1},\ldots\mspace{14mu},k_{i - 1}}\}}}{\arg\;\min}{\left( G_{i} \right)_{j}}^{2}}},} & (10)\end{matrix}$

wherein (G_(i))_(j) represents the j-th row of the matrix (G_(i)), ∥ ∥²represents 2 Norm of the matrix (G_(i))_(j),

$\underset{j \notin {\{{k_{1},\ldots\mspace{14mu},k_{i - 1}}\}}}{\arg\;\min}{\left( G_{i} \right)_{j}}^{2}$stands for j corresponding to the minimum value of the target function∥(G_(i))_(j)∥² in the case that j does not belong to k₁, . . . ,k_(i−1).

2) calculating a zero-forcing vector:w _(k) _(i) =(G _(i))_(k) _(i)   (11)

3) calculating the decision estimated valuey _(k) _(i) =w _(k) _(i) ·r _(i)  (12)

4) obtaining the detection component â_(k) _(i) of the transmittingsymbol vector aâ _(k) _(i) =Q(y _(k) _(i) )  (13)

5) taking the detection component as a known signal and canceling itfrom the receiving symbol vector:r _(i+1) =r _(i) −â _(k) _(i) ·(H)_(k) _(i)   (14)

6) calculating a new initial value used for the next iteration:{tilde over (H)}={tilde over (H)} _(k) _(i)   (15)G _(i+1) ={tilde over (H)} ⁺  (16)i=i+1  (17)

where {tilde over (H)} _(k) _(i) represents that the k_(i) th column ofthe matrix {tilde over (H)} is set to zero. It should be noted that thenew Moore-Penrose pseudoinverse obtained from the equation (16) is basedon the “reduced” H, where the k₁,k₂, . . . ,k_(i)-th columns havealready been set to zero. The column that is set as zero corresponds tothe component of a as detected, thereby canceling the components of thetransmitting symbol vector a which have been detected from the receivingsymbol vector. At this time, the system becomes a system of removingtransmitting antennae k₁,k₂, . . . ,k_(i), or equals to a system ofa_(k) ₁ = . . . =a_(k) _(i) =0.

This method uses the interference cancellation technology so that thespace diversity degrees of the symbols that are detected in sequence are1, 2, . . . M respectively.

It can be seen from the above Ordering-SIC V-BLAST detection method thatthis method needs to perform Moore-Penrose pseudoinverse to the channelmatrix for M (the number of the transmitting antennae) times, each timeobtaining a zero-forcing vector, and then carrying out an orderingoperation. Therefore, this method is relatively complicated in case ofcomparatively many transmitting antennae. In addition, the performanceof error ratio of the method is much restricted due to error propagationbetween layers of V-BLAST.

On the basis of the aforesaid Ordering-SIC V-BLAST detection method, animproved detection method was proposed in an article titled “Detectionalgorithm improving V-BLAST performance over error propagation”(hereinafter referred to as D2) by Cong Shen, Hairuo Zhuang, Lin Dai andShidong Zhou in 2003.

First of all, in this method, the Ordering-SIC V-BLAST detection methoddisclosed by D1 is used to detect, with respect to a transmitting symbolvector a of a V-BLAST system having M transmitting antennae and Nreceiving antennae, M detection components that are respectivelyrepresented as â_(M) ⁰,â_(M−1) ⁰, . . . ,â₂ ⁰,â₁. Here the optimumdetection order is assumed to be M, M−1, . . . , 1.

After that, iteration steps begin. In the first loop of this iterationsteps, the detection component â₁ with the highest space diversitydegree among the detection components of the current transmitting symbolvector a is cancelled from the receiving symbol vector as a knownsignal, then the residual (M−1, N) system with M−1 transmitting antennaeand N receiving antennae is further detected using the Ordering-SICV-BLAST detection method to obtain the first detection estimate â_(M)¹,â_(M−1) ¹, . . . ,â₂ ¹ of the transmitting symbol vector a. The firstdetection estimate together with the above known signal â₁ forms thefirst update estimate â_(M) ¹,â_(M−1) ¹, . . . ,â₂ ¹,â₁. The first loopends.

Then, the second loop is executed. In the second loop, both the signalâ₁ and the signal â₂ ¹ with the highest space diversity degree among thedetection estimate â_(M) ¹,â_(M−1) ¹, . . . ,â₂ ¹,â₁ are cancelled fromthe receiving symbol vector as known signals, then the residual (M−2, N)system with M−2 transmitting antennae and N receiving antennae isfurther detected using the Ordering-SIC V-BLAST detection method toobtain the second detection estimate â_(M) ²,â_(M−1) ², . . . ,â₃ ² ofthe transmitting symbol vector component. The second detection estimatetogether with the above known signals â₁ and â₂ ¹ form the second updateestimate â_(M) ²,â_(M−1) ², . . . ,â₃ ²,â₂ ¹,â₁. Similar performancesare executed till the (M−1)-th update estimate â_(M) ^(M−1),

â_(M − 1)^(M − 2), …  , â₂¹,â₁ is obtained. This (M−1)-th update estimate is just the finaldetection result.

The V-BLAST detection method disclosed by D2 can, over the Ordering SICV-BLAST detection method disclosed by D1, further reduce errorpropagation between the V-BLAST layers, so that the detectingperformance of V-BLAST is improved to a certain extent. However, thedetecting procedure is too complicated, and still has inter-layer errorpropagation. Its error performance is still restricted to a certainextent.

SUMMARY OF THE INVENTION

With regard to the aforesaid two existing detection methods, the presentinvention proposes a V-BLAST detection method capable of furtherreducing V-BLAST inter-layer error propagation so that the error codeperformance can be further improved.

According to the V-BLAST detection method for a MIMO system, including:

a first detecting step for acquiring in sequence the old detectioncomponents of a transmitting symbol vector with the optimumordering-successive interference cancellation detection method;

a second detecting step for taking the detection component with thehighest space diversity degree among the old detection components as afirst new detection component, and acquiring in sequence the other newdetection components of the transmitting symbol vector in an inverseorder of optimum detection order with the optimum ordering-successiveinterference cancellation detection method;

an outputting step for outputting the first new detection component andthe other new detection components as the final detection result.

The present invention also provides a V-BLAST detection device for aMIMO system, including:

a first detecting means for acquiring in sequence the old detectioncomponents of a transmitting symbol vector with the optimumordering-successive interference cancellation detection method;

a second detecting mean for selecting the detection component with thehighest space diversity degree among the old detection components as afirst new detection component, and acquiring in sequence the other newdetection components of the transmitting symbol vector in an inverseorder of the optimum detection order with the optimumordering-successive interference cancellation detection method;

an outputting means for outputting the first new detection component andthe other new detection components as the final detection result.

The present invention also provides a receiving device at network sidecomprising the above-mentioned V-BLAST detection device.

The present invention also provides a receiving device at user sidecomprising the above-mentioned V-BLAST detection device.

The V-BLAST detection method and the V-BLAST detection device accordingto the present invention can suppress the inter-layer error propagationof V-BLAST better and hence remarkably improve the error codeperformance of V-BLAST.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a MIMO system based on V-BLAST scheme;

FIG. 2 is a flow chart of a V-BLAST detection method according to theinvention;

FIG. 3 is a detailed flow chart of the comparing step in the V-BLASTdetection method according to the invention shown in FIG. 2;

FIG. 4 is a schematic diagram of the structure of the V-BLAST detectiondevice according to the invention;

FIG. 5 illustrates an emulate effect diagram of the V-BLAST detectionmethod according to the invention, the Ordering-SIC V-BLAST detectionmethod disclosed by D1 and the V-BLAST detection method disclosed by D2.

PREFERRED EMBODIMENTS

The V-BLAST detection method and device according to the invention willbe described in detail in conjunction with the drawings.

FIG. 1 shows a MIMO system in which signals are detected with theV-BLAST detection method according to the invention. As stated above,this system has M transmitting antennae and N receiving antennae,wherein 1<M≦N. Within a symbol time, a1,a2, . . . ,aM are used torepresent the components of the transmitting symbol vector a transmittedfrom the transmitting antennae respectively, wherein the transmittingsymbol vector a=(a₁,a₂, . . . ,a_(M))^(T)represents a vector with M rowsand 1 column obtained by transposing the vector (a₁,a₂, . . . ,a_(M)).

The V-BLAST detection method according to the invention is, on the basisof the aforesaid Ordering-SIC V-BLAST detection method, realized byfurther introducing outer close loop iteration steps. FIG. 2 shows aflow chart of the V-BLAST detection method according to the invention.

As shown in FIG. 2, the method starts at step 201. In step 202, theinitial value of iteration times is set as 0.

After that, the procedure comes to step 203. In step 203, the firstdetection component of the transmitting symbol vector a is, above all,detected by using the above Ordering-SIC V-BLAST detection methodaccording to the optimum detection order. The first detection componentof the transmitting symbol vector a that is firstly detected isrepresented as â_(M) ^(old), which serves as the first referencecomponent. In this step, the optimum detection order is represented ask₁,k₂, . . . ,k_(M−1)M,k_(M), a certain permutation of M, M−1, . . . ,2, 1. In this embodiment, the optimum detection order is assumed to beM, M−1, . . . 2, 1.

Then, the procedure comes to step 204. In step 204, based on the firstdetection component as detected in step 203, i.e. the first referencecomponent â_(M) ^(old), other detection components are detected insequence by using Ordering-SIC V-BLAST detection method according to theoptimum detection order. The other detection components, which arerepresented as

â_(M − 1)^(old), …  , â₂^(old),â₁, together with the first detection component â_(M) ^(old), form thedetection components of the transmitting symbol vector, represented as

â_(M)^(old), â_(M − 1)^(old), …  , â₂^(old), â₁.

Next, the procedure shown in FIG. 2 comes to step 205. In step 205,based on the detection components of the transmitting symbol vectordetected in steps 203 and 204, the detection component â₁ with thehighest space diversity degree, which is taken as a known signal, iscancelled from the receiving symbol vector r by using the aboveOrdering-SIC V-BLAST detection method. And other detection components ofthe transmitting symbol vector are detected in sequence in an inverse ofthe optimum detecting sequence. The other detection components arecalled as other new detection components and represented as

â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new),wherein â_(M) ^(new) is a new detection component that is finallydetected and is named as the second reference component. Thus, the firstiteration is completed. The aforesaid detection component â₁ with thehighest space diversity degree served as a known signal and theaforesaid other new detection components

â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new)constitute in common the new detection components of the transmittingsymbol vector, which are represented as â₁, â₂ ^(new), . . . ,

â_(M − 1)^(new), â_(M)^(new).After that, the procedure comes to step 206. In step 206, the times ofiteration augment 1. After step 206, the procedure comes to thecomparing and processing step 207.

In the comparing and processing step 207, the new detection componentthat is finally detected in step 205, i.e. the second referencecomponent â_(M) ^(new), is compared with the first detection componentthat is firstly detected in step 203, i.e. the first reference componentâ_(M) ^(old). When both are not equal, it is further decided whether thetimes of iteration is already greater than or equal to the predeterminedtimes of iteration, and the corresponding processing is respectivelycarried out according to respective result of comparison and decision.

The procedure shown in FIG. 2 ends at step 208.

The detailed steps of the comparing and processing step 207 shown inFIG. 2 are illustrated in FIG. 3. Step 207 includes step 2071 to step2074. In step 2071, the second reference component â_(M) ^(new) iscompared with the first reference component â_(M) ^(old) to see whetherthey are equal. When both are equal, the procedure comes to step 2072.In step 2072, the new detection components

â_(M)^(new), â_(M − 1)^(new), …  , â₂^(new),,â₁, of the transmitting symbol vector that is obtained in outputtingstep 205 are taken as the final detection result. Step 207 ends. Whenthe second reference component â_(M) ^(new) is not equal to the firstreference component â_(M) ^(old) in step 2071, the procedure comes tostep 2073. In step 2073, it is determined whether the times of iterationis already greater than or equal to the predetermined times ofiteration. When it is decided the time of iteration is already greaterthan or equal to the predetermined times of iteration, the procedurecomes to step 2072. Otherwise, the procedure comes to step 2074. In step2074, the second reference component â_(M) ^(new) is changed to be a newfirst reference component â_(M) ^(old)′. After that, the procedurereturns to step 204 shown in FIG. 2. In step 204, the followingdetection is carried out as the new first reference component â_(M)^(old)′ being the first detection component.

It can be seen from the above description that the space diversitydegrees of the new detection components

â_(M)^(new), â_(M − 1)^(new), …  , â₂^(new)of the transmitting symbol vector that are obtained in step 205 of eachiteration according to the V-BLAST detection method of the invention arehigher than those of the detection components

â_(M)^(old), â_(M − 1)^(old), …  , â₂^(old)of the transmitting symbol vector that are obtained in step 204, so theformer has an accuracy higher than the latter. When both have differentdetection results, the latter is replaced by the former. And on thisbasis the whole detection procedure is repeated to form a close loopiteration, such that the accuracy of the detection can be furtherimproved. When both have the same detection results, the iterationprocedure is terminated.

It should be understood that in the procedure shown in FIG. 2, step 202,step 206 and step 2073 in step 207 for calculating the time of iterationand deciding only serve as auxiliary steps of the iteration detectionprocedure. These steps do not intend to restrict the detection method ofthe invention. Preferably, in actual application, the times of iterationmay be set to guarantee the convergence of iteration procedure in orderto prevent the unanticipated situation of non-convergent iteration. Forexample, the times of iteration is set as one of 2-10, preferably as 3.

The present invention also provides a V-BLAST detection device. FIG. 4is a schematic diagram showing the structure of the V-BLAST detectiondevice 300 according to the invention. It can be seen from FIG. 4 thatthe V-BLAST detection device 300 according to the invention comprises anoptimum ordering means 301, an iteration detecting means 302 and acomparing and outputting means 303.

The receiving symbol vector r and the channel matrix H are input to theoptimum ordering means 301. The optimum ordering means 301 obtains theoptimum detection order according to the optimum ordering method andsends the optimum detection order to the iteration detecting means 302,wherein the optimum detection order is represented as k₁,k₂, . . .,k_(M−1),k_(M), a certain permutation of M, M−1, . . . 2, 1. In thisembodiments, the optimum detection order is assumed to be M, M−1, . . .2, 1.

The iteration detecting means 302 detects in sequence M detectioncomponents of the transmitting symbol vector by using the Ordering-SICV-BLAST detection method disclosed in D1 according to the optimumdetection order obtained from the optimum ordering means 301. The Mdetection components are represented as

â_(M)^(old), â_(M − 1)^(old), …  , â₂^(old), â₁,wherein the first detection component of the transmitting symbol vectorthat is firstly detected is represented as â_(M) ^(old) and serves asthe first reference component.

Then, the iteration detecting means 302 cancels the detection componentâ₁ with the highest space diversity degree among the aforesaid detectedM detection components

â_(M)^(old), â_(M − 1)^(old), …  , â₁,which as a known signal, from the receiving symbol vector r. And otherdetection components of the transmitting symbol vector are detected insequence in an inverse of the received optimum detection order by usingthe aforesaid Ordering-SLC V-BLAST detection method. The other detectioncomponents are called as other new detection components and arerepresented as

â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new),wherein â_(M) ^(new) is a new detection component that is finallydetected and is named as the second reference component. The aforesaiddetection component â₁ that is firstly cancelled as a known signal andthe aforesaid other new detection components

â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new)constitute in common the new detection components of the transmittingsymbol vector, which are represented as

â₁, â₂^(new), …  , â_(M − 1)^(new), â_(M)^(new).The iteration detecting means 302 completes iteration calculation once.The iteration detecting means 302 transmits the first referencecomponent â_(M) ^(old) and the second reference component â_(M) ^(new)to the comparing and outputting means 303.

In the comparing and outputting means 303, the second referencecomponent â_(M) ^(new) is compared to the first reference componentâ_(M) ^(old). If both are equal, the comparing and outputting means 303reads from the iteration detecting means 302 the new detectioncomponents â₁,

â₂^(new), …  , â_(M − 1)^(new), â_(M)^(new)of the transmitting symbol vector and outputs them as the finaldetection result. When both are not equal, the comparing and outputtingmeans 303 feeds the second reference component â_(M) ^(new) into theiteration detecting means 302 as a new first reference component â_(M)^(old)′. The iteration detecting means 302 takes this new firstreference component â_(M) ^(old)′ as the first detection componentduring detection. The following detection is carried out according tothe aforesaid operation.

It should be understood that the above operation of feeding the newfirst reference component â_(M) ^(old)′ into the iteration detectingmeans 302 can also be carried out by the comparing and outputting means303 sending an instruction of changing the first reference componentâ_(M) ^(old) to the iteration means 302 and then the iteration detectingmeans 302 changing it according to the instruction. The specific way inwhich the iteration detecting means 302 obtains a new first referencecomponent does not constitute restriction to the present invention.

The V-BLAST detection device 300 according to the invention shown inFIG. 4 may also include iteration times calculating means 304 thatcalculates the times of iteration and thereby controls the procedure ofV-BLAST detection. As shown in FIG. 4, iteration detecting means 302will feed an instruction of increasing the times of iteration into theiteration times calculating means 304 after each iteration calculationis completed, then the iteration times calculating means 304 adds one tothe times of iteration recorded therein.

When the comparing and outputting means 303 makes comparison, it will,first of all, compare the second reference component â_(M) ^(new) andthe first reference component â_(M) ^(old). When both are not equal, thecomparing and outputting means 303 reads the times of iteration recordedin the iteration times calculating means 304, and decides whether therecorded times of iteration is greater than or equal to thepredetermined times of iteration. When the recorded times of iterationis equal to or greater than the predetermined times of iteration, thecomparing and outputting means 303 reads from the iteration detectingmeans 302 the new detection components

â₁, â₂^(new), …  , â_(M − 1)^(new), â_(M)^(new)of the transmitting symbol vector and outputs them as the finaldetection result. When the times of iteration recorded in the iterationtimes calculating means 304 is less than the predetermined times ofiteration, the comparing and outputting means 303 will feed the secondreference component â_(M) ^(new) into the iteration detecting means 302as a new first reference component â_(M) ^(old)′. The iterationdetecting means 302 takes this new first reference component â_(M)^(old)′ as the first detection component during detection. The followingdetection is carried out according to the aforesaid operation.

In comparison with the prior detection method, the V-BLAST detectionmethod and device according to the invention can suppress inter-layererror propagation of V-BLAST better. Thereby the error code performanceof V-BLAST can be improved greatly, which can be verified in computeremulation. At the same time, although the complexity of calculation ofthe V-BLAST detection method according to the invention is almostdoubled over the aforesaid Ordering-SLC V-BLAST detection method, theerror code performance is remarkably improved. In comparison with theV-BLAST detection method disclosed by D2, however, the complexity ofV-BLAST detection method according to the invention is reduced to acertain extent.

The emulation results of the above three V-BLAST detection methods areshown in FIG. 5. During emulation, a V-BLAST with four transmittingantennae and four receiving antennae is adopted. The MIMO channel is aflat independent Rayleigh fading channel and the category ofconstellation modulation is QPSK. No channel encoding is used duringemulation. The maximum times of iteration is set to be 3. It can be seenfrom this figure that when BER is 0.0001, the performance of the V-BLASTdetection method according to the invention is increased about 3 dB thanthat of the V-BLAST detection method disclosed by D2, while increasedabout 5 dB than that of the Ordering-SLC V-BLAST detection method.Therefore, in comparison with these existing detection methods, theerror code performance of the V-BLAST detection method and deviceaccording to the invention can be greatly improved.

On the other hand, where the complexity of method is concerned, it canbe seen from the description of FIG. 2 that the V-BLAST detection methodaccording to the invention enables, on the basis of the Ordering-SLCV-BLAST detection method, the Moore-Penrose pseudoinverse operation of azero H matrix as calculated in the first iteration to be used repeatedlyin the following iteration(s). Therefore, where a V-BLAST with fourtransmitting antennae and four receiving antennae is concerned, it needsseven times of operations for calculating the Moore-Penrosepseudoinverse. The V-BLAST detection method disclosed by D2 needs tentimes of operations for calculating the Moore-Penrose pseudoinverse. TheMoore-Penrose pseudoinverse operation accounts for most of the totalcomplexity. Meanwhile, the computer emulation indicates that the timesof iteration of outer close loop are generally small, which is about oneto three times. Therefore, in comparison with the V-BLAST detectionmethod disclosed by D2, the V-BLAST detection method and deviceaccording to the invention has a reduced complexity to a certain extent.

Various other changes and modifications can be made without departingfrom the scope and spirit of the present invention. It should beunderstood that the invention is not limited to particular embodiments,the scope of the invention is defined by the appended claims.

1. A V-BLAST (Vertical Bell Laboratories Space-Time codes) detection method for a MIMO (Multiple Input Multiple Output) system, including: a first detecting step for acquiring in sequence the old detection components (â_(M)^(old), â_(M − 1)^(old), …  , â₁, where  M  is  an  integer)  of a transmitting symbol vector (a) with the optimum ordering-successive interference cancellation detection method; a second detecting step for taking the detection component (â₁) with the highest space diversity degree among the old detection components (â_(M)^(old), â_(M − 1)^(old), …  , â₁)  as a first new detection component, and acquiring in sequence other new detection components (â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new))  of said transmitting symbol vector (a) in an inverse order of optimum detection order with the optimum ordering-successive interference cancellation detection method; an outputting step for outputting said first new detection component (â₁) and said other new detection components (â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new))  as the final detection result.
 2. The detection method according to claim 1, further includes between the second detecting step and the outputting step: a first comparing step for comparing the first old detection component (â_(M) ^(old)) which is firstly acquired in the first detecting step and the last new detection component (â_(M) ^(new)) which is finally acquired in the second detecting step; a first replacing step for making said first old detection component (â_(M) ^(old)) equal to the value of the last new detection component (â_(M) ^(new)) if the first old detection component (â_(M) ^(old)) is not equal to the last new detection component (â_(M) ^(new)) and then returning to said first detecting step, otherwise coming to said outputting step.
 3. The detection method according to claim 1, further includes between the second detecting step and the outputting step: a second comparing step for comparing the times of performing the first detecting step and the second detecting step and a predetermined times of iteration; a second replacing step for making said first old detection component (â_(M) ^(old)) equal to the value of the last new detection component (â_(M) ^(new)) if the times of performing the first detecting step and the second detecting step is less than the predetermined times of iteration and then returning to said first detecting step, otherwise coming to said outputting step.
 4. The detection method according to claim 3, wherein said predetermined times of iteration is set to be any one of 2-10.
 5. The detection method according to claim 4, wherein said predetermined times of iteration is set to be
 3. 6. The detection method according to any of claims 1-5, wherein said second detecting step comprises the steps of: canceling said first new detection component (â₁) as a known signal from the current receiving symbol vector (r), the resultant receiving symbol vector then being the current receiving symbol vector (r); setting, in an inverse order of the optimum detection order, a column in the channel matrix corresponding to said known signal component as zero to obtain a zero channel matrix and further acquiring a Moore-Penrose pseudoinverse channel matrix of said zero channel matrix; forming a linear combination of said current receiving symbol vector(r) with the column vector of said Moore-Penrose pseudoinverse channel matrix corresponding to the next detection component just following said known signal to obtain an estimated value of said detection component; constellation demodulating the estimated value of said detection component to obtain said detection component of said transmitting symbol vector (a) and taking it as a known signal; and repeating the above steps and obtaining in sequence said other new detection components (â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new))  of said transmitting symbol vector (a).
 7. A V-BLAST (Vertical Bell Laboratories Space-Time codes) detection device for a MIMO (Multiple Input Multiple Output) system, including: a first detecting means for acquiring in sequence the old detection components (â_(M)^(old), â_(M − 1)^(old), …  , â₁, where  M  is  an  integer)  of a transmitting symbol vector (a) with the optimum ordering-successive interference cancellation detection method; a second detecting mean for selecting the detection component (â₁) with the highest space diversity degree among the old detection components (â_(M)^(old), â_(M − 1)^(old), …  , â₁)  as a first new detection component, and acquiring in sequence other new detection components (â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new))  of said transmitting symbol vector (a) in an inverse order of the optimum detection order with the optimum ordering-successive interference cancellation detection method; an outputting means for outputting said first new detection component (â₁) and said other new detection components (â₂^(new), â₃^(new), …  , â_(M − 1)^(new), â_(M)^(new))  as the final detection result.
 8. The detection device according to claim 7, further comprising: a first comparing means for comparing the first old detection component (â_(M) ^(old)) which is firstly acquired in the first detecting means and the last new detection component (â_(M) ^(new)) which is finally acquired in the second detecting means; a first replacing means for making said first old detection component (â_(M) ^(old)) equal to the value of the last new detection component (â_(M) ^(new)) if the first old detection component (â_(M) ^(old)) is not equal to the last new detection component (â_(M) ^(new)) and then sending the resultant new first old detection component (â_(M) ^(old)) to the first detecting means, which will performs iteration detections together with the second detecting means, otherwise transmitting to said outputting means an instruction signal for outputting the final detection result.
 9. The detection device according to claim 7, further comprising: a second comparing means for comparing the detection times performed by the first detecting means together with the second detecting means and a predetermined times of iteration; a second replacing means for making said first old detection component (â_(M) ^(old)) equal to the value of the last new detection component (â_(M) ^(new)) if the detection times performed by the first detecting means and the second detecting means is less than the predetermined times of iteration and then sending the resultant new first old detection component (â_(M) ^(old)) to the first detecting means, which will performs iteration detections together with the second detecting means, otherwise transmitting to said outputting means an instruction signal for outputting the final detection result.
 10. The detection device according to claim 9, wherein said predetermined times of iteration is set to be any one of 2-10.
 11. The detection device according to claim 10, wherein said predetermined times of iteration is set to be
 3. 12. A receiving device at network side comprising the V-BLAST detection device as claimed in claim
 7. 13. A receiving device at user side comprising the V-BLAST detection device as claimed in claim
 7. 